A digital cross-connect system (DSX) provides a location for interconnecting two digital transmission paths. The apparatus for a DSX is located in one or more frames, generally referred to as bays, usually in a telephone central office. The DSX apparatus also provides jack access to the transmission paths to trace a transmission path through the DSX.
DSX jacks are well known and typically include a plurality of bores sized for receiving plugs. U.S. Pat. No. 5,170,327, assigned to the present assignee, describes such a jack. The jacks are typically electrically connected to digital transmission lines, and are also electrically connected to a plurality of wire termination members used to cross-connect the jacks. By inserting plugs within the bores of the jacks, signals transmitted through the jacks can be traced as is well known. If a technician wants to know what a particular piece of equipment is coupled to through the DSX, the technician would insert a plug into a monitor bore of the jack coupled to that particular piece of equipment and look for a flashing light located on a second jack which is coupled to an end piece of equipment, i.e., the cross-connected equipment. This allows the technician to trace the transmission path through the DSX and determine what equipments are coupled together.
Each tracer lamp is located on a particular shelf in a particular row of a particular bay. There are generally several bays in any communications office. Typically, the tracer lamp only flashes for about 45 seconds. In a small central office this may be enough time to give the technician to find the other end of the circuit. In larger central offices with many bays, however, this is not enough time since the technician is not directed to any particular bay and thus must check each one until he discovers the illuminated tracer lamp. In both cases, tracing a transmission path is time consuming and tedious.
U.S. Pat. No. 5,418,334 describes a relative position tracer lamp to indicate to a technician which shelf or rack to find the flashing tracer lamp indicator thereby reducing the technician's search for the flashing tracer lamp. The particular implementation described in this patent, however, suffers from several disadvantages. First, the circuitry employed requires a separate DC power source which makes it undesirable in a central office environment in which -48 volts is the available power supply. In addition, an intrusive technique, i.e., serial connection, is used to couple a transformer to a particular tracer wire thereby making it cumbersome to implement because of the direct wiring necessary.
Thus, it is desirable to provide a relative indicator that does not require its own power supply. In addition, it is desirable to provide a relative indicator that utilizes a non-intrusive method of detecting current change in a bay. Also, it is desirable to provide a relative indicator that reduces the overall effort and amount of wiring to be performed during installation.